Directory enquiry (DQ) services for wireline telephones have been available for some years. The usual interface to such a service is to telephone a directory enquiries operator, and provide a name of a person for which the corresponding telephone number is desired. Directory enquiries is an established and profitable service for land lines in the UK, and the service has proved relatively easy to deploy for a number of reasons, as outlined below.
Firstly, at least within the UK there is a dominant operator, and hence the majority of numbers are accessible from a single source. This means that the “critical mass” of available numbers required for a successful DQ service is easily achieved.
Secondly the phones are tied to a location. Thus, phone numbers can be easily categorised according to address and duplicate names can be disambiguated. Where multiple name matches are obtained the DQ operator can ask for additional information such as geographical information to differentiate the multiple matches.
Thirdly, the details of the telephone line's owner are always known, as it is necessary to provide identification details and an address at which the telephone line is to be installed.
In contrast to the DQ situation for wireline telephone lines the corresponding provision of DQ services for mobile telephones is much less straightforward, as there are a number of complicating factors, as outlined next.
Firstly in many countries there is no dominant operator, and hence it is difficult to create the “critical mass” of registered users necessary to provide a comprehensive DQ service. In the UK for example customers are relatively evenly split between 4 main operators and a comprehensive directory necessitates agreement between these operators.
Secondly, by their nature mobile telephones are not tied to a particular address and thus categorisation by address is less appropriate. This leads to problems in resolving duplicate names, as geographical information cannot then be used to differentiate between multiple results.
Thirdly a further problem arises due to the ability of mobile telephone users to have “Pre-pay” or “Pay-as-you-go” price plans. For example the majority of mobile telephones purchased in the UK are pre-pay telephones and are typically purchased anonymously. In many cases it is therefore not possible for the network operators to know the identities of the majority of their customers. Without such identity information it becomes very difficult to compile a comprehensive enough directory of names and numbers to allow a DQ service to be offered.
The absence of a centralised DQ service for mobile telephones is presently alleviated somewhat by the provision of name and number memory stores on the mobile telephone handsets themselves, commonly known as “Address Books”. Here a mobile telephone user can store the names and associated mobile and/or fixed-line telephone numbers of all of his family, friends and other acquaintances. In use the user can select the number for a particular person direct from the telephone address book for dialing by the telephone.
The mere provision of mobile telephone address books in itself provides additional problems, however, as if a mobile telephone is lost or stolen then all the numbers stored within the address book will at worst need to be gathered again, or at best need to be entered into a new mobile telephone. Moreover, it is quite common for mobile telephone users to change their telephones on a regular basis, and frequently this is most economically achieved by taking a new connection with a new number. This necessitates a user having to communicate her new number to those people who she wishes to have it, and those people updating their telephone address books. Similarly, due to this “number churn” the numbers stored in any particular user's mobile telephone address book may not be current as other users may have changed their telephones without notifying the user.
In unrelated art, in the 1960's Stanley Milgram in “The Small World Problem”, Psychology Today 1(1):60-76 showed that any two randomly chosen individuals in the United States are linked by a chain of six or fewer first-name acquaintances. This concept has been popularised generally as the well known “six degrees of separation” concept, or “small-world” theory. The concept has been applied in the past to the problem of expert referrals, and Kautz H et al. in “The Hidden Web”, Al Magazine, Summer 1997, American Association of Al, pp. 27-36 describe an expert referral system applied to the field of Al experts.